netdev - [PATCH net-next] ipv6: tcp: send consistent autoflowlabel in TIME

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Message-Id: <20190609005851.32243-1-edumazet@google.com>
Date:   Sat,  8 Jun 2019 17:58:51 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next] ipv6: tcp: send consistent autoflowlabel in
 TIME_WAIT state

In case autoflowlabel is in action, skb_get_hash_flowi6()
derives a non zero skb->hash to the flowlabel.

If skb->hash is zero, a flow dissection is performed.

Since all TCP skbs sent from ESTABLISH state inherit their
skb->hash from sk->sk_txhash, we better keep a copy
of sk->sk_txhash into the TIME_WAIT socket.

After this patch, ACK or RST packets sent on behalf of
a TIME_WAIT socket have the flowlabel that was previously
used by the flow.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/inet_timewait_sock.h |  1 +
 net/ipv4/tcp_minisocks.c         |  1 +
 net/ipv6/tcp_ipv6.c              | 13 ++++++++++---
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index c2f756aedc5453576d67076b20b7c5fa0e64de8a..aef38c140014600dbf88b1d664bad1b0adf63668 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -70,6 +70,7 @@ struct inet_timewait_sock {
 				tw_flowlabel	: 20,
 				tw_pad		: 2,	/* 2 bits hole */
 				tw_tos		: 8;
+	u32			tw_txhash;
 	struct timer_list	tw_timer;
 	struct inet_bind_bucket	*tw_tb;
 };
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 7c35731816e23fe0f82351d3848bf13379efad5f..11011e8386dc97254a752514e4e6f77a068efaf4 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -283,6 +283,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
 			tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 			tw->tw_tclass = np->tclass;
 			tw->tw_flowlabel = be32_to_cpu(np->flow_label & IPV6_FLOWLABEL_MASK);
+			tw->tw_txhash = sk->sk_txhash;
 			tw->tw_ipv6only = sk->sk_ipv6only;
 		}
 #endif
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c1da52c7f990f2fa3e020e3f3a33934149ad225e..ad7039137a20f9ad8581d9ca01347c67aa8a8433 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -883,9 +883,16 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 		fl6.flowi6_oif = oif;
 	}
 
-	if (sk)
-		mark = (sk->sk_state == TCP_TIME_WAIT) ?
-			inet_twsk(sk)->tw_mark : sk->sk_mark;
+	if (sk) {
+		if (sk->sk_state == TCP_TIME_WAIT) {
+			mark = inet_twsk(sk)->tw_mark;
+			/* autoflowlabel relies on buff->hash */
+			skb_set_hash(buff, inet_twsk(sk)->tw_txhash,
+				     PKT_HASH_TYPE_L4);
+		} else {
+			mark = sk->sk_mark;
+		}
+	}
 	fl6.flowi6_mark = IP6_REPLY_MARK(net, skb->mark) ?: mark;
 	fl6.fl6_dport = t1->dest;
 	fl6.fl6_sport = t1->source;
-- 
2.22.0.rc2.383.gf4fbbf30c2-goog